If it can get in the 20's there, I would winterize. Putting a heater inside the camper will have little effect on water lines that run in/out to the tanks.
If you don't want to mess with it, search around for local RV repair people who are more than happy to come to you and winterize it for you. (We have one here and he's amazing....even replaced a friends awning for $400 when the dealer wanted over $1,000)
Rick & Karen
(Retired USAF, MSgt)
5-year Travel Trailer RVers
2013 Forest River Rockwood Ultra-Lite 2904SS
2014 Toyota Tundra Maxcrew SR-5 TRD 4x4